Upgrade u-boot to 2014.7 and sync with Xilinx master-next

Bring u-boot up to date and adjust board patches. Drop zynq-miami which
has been replaced with topic-miami.
miami-xilinx-sdk: Add NAND settings, remove dead code

Remove the version check, we'll never see old silicon, so don't waste
so much effort in supporting it.

Add NAND information to the pinmux and clock configuration. Don't
actually enable it though. This allows the bootloader to pick NAND
or QSPI later on.